Testopel ® vs. Generic Testosterone Pellets.

Inclusion Criteria: * Voluntarily sign and date the study consent form(s), which have been approved by an Institutional Review Board (IRB). Written consent must be obtained prior to the initiation of any study procedures. * Male between 18 and 75 years of age. * Documented diagnosis of primary hypogonadism (congenital or acquired) or hypogonadotropic hypogonadism (congenital or acquired). * Serum total testosterone \< 300 ng/dL on 2 measurements * Naïve to androgen replacement or has discontinued current treatment and completed a washout of 4 weeks following androgen treatment. * Judged to be in good general health as determined by the principal investigator based upon the results of a medical history, physical examination, vital signs, laboratory profile and a 12-lead electrocardiogram (ECG). Exclusion Criteria: * History of significant sensitivity or allergy to androgens, or product excipients. * Clinically significant findings in the pre-study examinations including abnormal breast examination requiring follow-up, abnormal ECG. * Abnormal prostate digital rectal examination (DRE) with palpable nodule(s) or International Prostate Symptom Score (I-PSS) score \> 19 points. * Body mass index (BMI) ≥ 40 kg/m2. * Clinically significant abnormal laboratory value, in the opinion of the investigator, in serum chemistry, hematology, or urinalysis including but not limited to: 1. Baseline hemoglobin \> 16 g/dL 2. Hematocrit \< 35% or \> 50% 3. prostate-specific antigen (PSA) \> 4 ng/mL * History of seizures or convulsions, including febrile, alcohol or drug withdrawal seizures. * History of any clinically significant illness, infection, or surgical procedure within 4 weeks prior to study drug administration. * History of stroke or myocardial infarction within the past 5 years. * History of, or current or suspected, prostate or breast cancer. * History of diagnosed, severe, untreated, obstructive sleep apnea. * History of abuse of alcohol or any drug substance in the opinion of the investigator within the previous 2 years. * Donation or loss of 550 mL or more blood volume (including plasmapheresis) or receipt of a transfusion of any blood product within 12 weeks prior to the start of treatment. * Inadequate venous access for collection of serial blood samples required for pharmacokinetic profiles. * Receipt of any investigational product within 4 weeks or within 5 half-lives prior to the start of treatment. * Inability to understand and provide written informed consent for the study.